GSL Code S is the bigger and one, it has 32 players and runs over the course of a couple months so that players can prepare for each match.

Super tournaments are shorter weekend events. They take place over a few days and have only 16 players (and less prize money/wcs points). They sort of bridge the gap between Code S seasons but aren't as important.

The term Code S as kind of lost relevancy since there is only one active "circuit" in the GSL. During GSL's hayday, there used to be Code S, which is the Major League/Premier League, and Code A, which was the Minor League/Challenger League of the GSL, with qualifiers feeding into Code A.

Now it is just GSL Code S with qualifiers, so the term "Code S" really doesn't mean anything anymore.

Creator of the patented 2-Lair-into-Getting-Slaughtered build in one of the worse games of Starcraft II I've played in recent memory in the LRTL.